Cathode single-sided region, cathode pole piece, secondary battery and electronic device

Abstract

The utility model relates to the technical field of batteries, in particular to a cathode single-sided area, a cathode pole piece, a secondary battery and an electronic device. The cathode single-sided region comprises a cathode current collector and a cathode active material layer coated on one surface of the cathode current collector, the cathode single-sided region is provided with a strip-shaped ripple-like array, the strip-shaped ripple-like array comprises a plurality of strip-shaped concave parts and a plurality of strip-shaped convex parts, the plurality of strip-shaped concave parts are arranged on the surface, far away from the cathode active material layer, of the cathode current collector, and the plurality of strip-shaped convex parts are arranged on the surface of the cathode current collector. The plurality of strip-shaped convex parts are arranged on the surface, far away from the cathode current collector, of the cathode active material layer; and the plurality of strip-shaped convex parts and the plurality of strip-shaped concave parts are in one-to-one correspondence. According to the cathode single-sided area structure, a dynamic counteracting mechanism is formed by a residual compressive stress field induced by micro-curved surface curvature and tensile stress generated by material expansion during electrochemical circulation.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a cathode single-sided area, cathode electrode, secondary battery, and electronic device. Background Technology

[0002] Silicon-carbon composite anode materials for lithium-ion batteries are considered a core technology for next-generation high-energy-density batteries due to their high theoretical specific capacity (3580 mAh / g) and low cost. However, the volume expansion effect of up to 300% during lithium insertion / extraction triggers dynamic reconstruction of the three-dimensional stress in the electrode system, leading to a significant stress concentration effect in the cell's radius (R-corner) region. From a micromechanical perspective, silicon particles undergo an amorphous to crystalline phase transition during lithiation, and their anisotropic expansion behavior generates shear stress at the electrode-current collector interface. Especially in the region of abrupt change in topological curvature at the cell's R-corner, the stress field exhibits a geometrical increase. This periodic mechanical load is transmitted to the aluminum foil substrate through the current collector-active material interface, inducing dislocation multiplication and slip band formation, ultimately leading to transgranular or intergranular brittle fracture of the aluminum foil. In particular, the aluminum foil in the single-sided area of ​​the cathode electrode is more prone to fracture. The single-sided area of ​​the cathode electrode is generally located on the outermost ring of the wound battery, and its current collector is only coated with active material on the side closest to the inside of the battery. When the aluminum foil breaks, the exposed active material comes into direct contact with the electrolyte, which can exacerbate side reactions and cause excessive growth of the SEI film at the interface, resulting in irreversible capacity decay and safety hazards. Utility Model Content

[0003] The primary objective of this invention is to overcome the shortcomings of the prior art and provide a single-sided cathode region to solve the technical problem that the single-sided region of the existing wound battery cathode electrode is prone to breakage.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A single-sided cathode region includes a cathode current collector and a cathode active material layer coated on one surface of the cathode current collector. The single-sided cathode region is provided with a striped corrugated array, which includes multiple striped recesses and multiple striped protrusions. The multiple striped recesses are disposed on the surface of the cathode current collector away from the cathode active material layer and are spaced apart along the length direction of the cathode current collector. The multiple striped protrusions are disposed on the surface of the cathode active material layer away from the cathode current collector and are spaced apart along the length direction of the cathode active material layer. The multiple striped protrusions and multiple striped recesses correspond one-to-one.

[0006] Furthermore, the structure of the single-sided region of the cathode satisfies the following relationship: S=(L1-L0) / 2h; 5%≤(L1-L0) / L0×100%≤10%;

[0007] Wherein, S is the number of the strip-shaped recesses or strip-shaped protrusions on the single-sided cathode region;

[0008] L1 is the length of the extended single-sided region of the cathode;

[0009] L0 is the length of the cathode single-sided region before extension;

[0010] H0 is the vertical distance from the lowest point of the strip-shaped recess to the plane of the cathode current collector that is away from the cathode active material layer.

[0011] Furthermore, the length L0 of the cathode single-sided region before extension is 100-200 mm; and / or,

[0012] The length L1 of the extended single-sided cathode region is 105-220 mm.

[0013] Furthermore, the number of the strip-shaped recesses is 13-2000; and / or the number of the strip-shaped protrusions is 13-2000.

[0014] Furthermore, the vertical distance from the lowest point of the strip-shaped recess to the plane of the cathode current collector away from the cathode active material layer is 5-200 μm; and / or, the vertical distance from the apex of the strip-shaped protrusion to the plane of the cathode active material layer away from the cathode current collector is 5-200 μm.

[0015] Furthermore, the cross-sections of the strip-shaped recess and the strip-shaped protrusion are elliptical or polygonal.

[0016] The second objective of this invention is to provide a cathode electrode sheet, which includes the aforementioned single-sided cathode region, wherein the single-sided cathode region is located at one end of the cathode electrode sheet along its length.

[0017] The third objective of this invention is to provide a secondary battery, including an electrode assembly, wherein the electrode assembly includes the aforementioned cathode electrode.

[0018] Furthermore, the electrode assembly is a wound electrode assembly, and the cathode single-sided area is located at the outermost ring of the electrode assembly.

[0019] The fourth objective of this invention is to provide an electronic device comprising the aforementioned secondary battery.

[0020] The beneficial effects of this invention are as follows: The cathode single-sided region structure of this invention is based on stress engineering for micro-processing of the cathode single-sided region. By constructing a strip-shaped corrugated array in the cathode single-sided region, micro-processing technology is used to simultaneously complete the single-sided prestress loading of the cathode during the wafer fabrication stage. This structure, through the residual compressive stress field induced by the curvature of the micro-curved surface, forms a dynamic cancellation mechanism with the tensile stress generated by material expansion during electrochemical cycling. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a side view of an embodiment of the present utility model;

[0023] Figure 2 This is a three-dimensional structural diagram of an embodiment of the present utility model.

[0024] Explanation of reference numerals in the attached figures: 10, single-sided area of ​​the cathode; 11, cathode current collector; 12, cathode active material layer; 13, strip-shaped recess; 14, strip-shaped protrusion; 20, cathode electrode. Detailed Implementation

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. For example, terms such as “length,” “width,” “upper,” “lower,” “left,” “right,” “front,” “rear,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer” indicate orientations or positions based on the orientations or positions shown in the accompanying drawings and are merely for ease of description and should not be construed as limiting the invention.

[0026] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this utility model are intended to cover non-exclusive inclusion; the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish different objects, not to describe a specific order. "A plurality of" means two or more, unless otherwise explicitly specified.

[0027] In the description, claims, and accompanying drawings of this utility model, when an element is referred to as "fixed to," "mounted to," "set on," or "connected to" another element, it can be directly or indirectly located on that other element. For example, when an element is referred to as "connected to" another element, it can be directly or indirectly connected to that other element.

[0028] Furthermore, the reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] It should be noted that, for ease of description, the three mutually perpendicular coordinate axes in space are defined as the X-axis, Y-axis, and Z-axis. The X-axis and Y-axis are two mutually perpendicular coordinate axes on the same horizontal plane, and the Z-axis is a vertical coordinate axis. The X-axis, Y-axis, and Z-axis are located in three mutually perpendicular planes in space, namely the XY plane, YZ plane, and XZ plane. The XY plane is a horizontal plane, and the XZ plane and YZ plane are both vertical planes, with the XZ plane perpendicular to the YZ plane.

[0030] Example

[0031] like Figure 1 and Figure 2 As shown, the present invention provides a cathode single-sided region 10, which includes a cathode current collector 11 and a cathode active material layer 12 coated on one surface of the cathode current collector 11. The cathode single-sided region 10 is provided with a strip-shaped corrugated array, which includes multiple strip-shaped recesses 13 and multiple strip-shaped protrusions 14. The multiple strip-shaped recesses 13 are disposed on the surface of the cathode current collector 11 away from the cathode active material layer 12, and the multiple strip-shaped recesses 13 are spaced apart along the length direction of the cathode current collector 11. The multiple strip-shaped protrusions 14 are disposed on the surface of the cathode active material layer 12 away from the cathode current collector 11, and the multiple strip-shaped protrusions 14 are spaced apart along the length direction of the cathode active material layer 12. The multiple strip-shaped protrusions 14 and the multiple strip-shaped recesses 13 correspond one-to-one.

[0032] The cathode single-sided region 10 structure of this invention is based on stress engineering and micro-processing of the cathode single-sided region 10. By constructing a strip-shaped corrugated array in the cathode single-sided region 10, micro-processing technology is used to simultaneously complete the pre-stress loading on one side of the cathode during the wafer fabrication stage. This structure, through the residual compressive stress field induced by the curvature of the micro-curved surface, forms a dynamic cancellation mechanism with the tensile stress generated by material expansion during electrochemical cycling. When a cathode electrode containing the cathode single-sided region of this invention is applied to a silicon-carbon system, the cathode does not break during cycling and can store more electrolyte.

[0033] The cathode single-sided region 10 structure of this invention can effectively alleviate stress concentration and improve structural stability. During the lithium insertion / deintercalation process of silicon-carbon composite anode materials, the anisotropic stress generated by volume expansion easily leads to shear stress concentration at the electrode-current collector interface, especially in geometrically abrupt regions such as the cell's radius (R-angle). This invention, by introducing a striped, corrugated array structure, can absorb and disperse the periodic mechanical load caused by volume changes, thereby significantly reducing the tendency of dislocation multiplication and slip band formation in the cathode current collector 11 substrate, suppressing the transgranular or intergranular fracture behavior of the cathode current collector 11, and improving the overall mechanical stability and cycle life of the electrode.

[0034] The cathode single-sided region 10 structure of this invention can optimize the stress transmission path and reduce the risk of damage to the current collector. The strip-shaped corrugated array structure, through its periodic geometric features, constructs a discontinuous and buffered stress transmission path between the current collector and the active material, so that the expansion stress does not concentrate in a single area. It is especially suitable for mechanically weak areas such as the single-sided region of the cathode electrode 20, where there is active material on only one side and no support on the other side, thereby effectively protecting the cathode current collector 11 from damage.

[0035] The cathode single-sided region 10 structure of this invention can enhance the interfacial bonding strength and inhibit the shedding of active material. The strip-shaped corrugated array structure of this invention increases the contact area and mechanical interlocking effect between the active material layer and the current collector, which helps to improve the interfacial bonding force between the two, further preventing the active material peeling phenomenon caused by repeated volume changes, and ensuring the long-term electrochemical performance stability of the battery.

[0036] The cathode single-sided region 10 structure of this invention can suppress excessive growth of the SE I film, thereby improving battery safety and cycle performance. By suppressing the exposure of active materials caused by the breakage of the cathode current collector 11, the direct contact opportunity between the active material and the electrolyte is reduced, thus effectively curbing the occurrence of side reactions and abnormal thickening of the SE I film, reducing irreversible capacity loss, and improving battery safety and cycle stability.

[0037] Further, the cathode current collector 11 is a metal current collector or a metal-containing composite current collector. In this embodiment, the metal current collector may be aluminum foil. The metal-containing composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The metal-containing composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). Specifically, in this embodiment, the cathode current collector 11 is aluminum foil. Aluminum foil, as a commonly used cathode current collector 11 material in lithium-ion batteries, has good conductivity, processing performance, and good compatibility with active materials. It is particularly suitable for high specific capacity silicon-carbon composite anode systems, which can effectively ensure electron transport efficiency and improve the overall electrochemical performance of the battery.

[0038] Specifically, the cathode electrode 20 includes a current collector and an active material layer coated on the surface of the current collector. The current collector includes a connected double-sided region and a single-sided region. Both surfaces of the double-sided region of the current collector are coated with the active material layer, and one surface of the single-sided region is coated with the active material layer. The cathode single-sided region 10 of this invention is the current collector single-sided region of the cathode electrode 20, and the cathode active material layer 12 is coated on one surface of the current collector single-sided region. In the electrode assembly of the wound battery, the cathode single-sided region 10 is located on the outermost ring of the wound battery electrode assembly. The side of the cathode single-sided region 10 coated with the cathode active material layer 12 faces the center of the electrode assembly, and the side of the cathode single-sided region 10 not coated with the cathode active material layer 12 faces the outside of the electrode assembly.

[0039] In this embodiment, the length direction of the cathode current collector 11 and / or the length direction of the cathode active material layer 12 are the winding direction of the wound battery electrode assembly, while the direction parallel to the central axis of the wound battery electrode assembly is the width direction of the cathode current collector 11 and / or the cathode active material layer 12.

[0040] In this embodiment, multiple strip-shaped recesses 13 extend along the width direction of the cathode current collector 11, and the two ends of the multiple strip-shaped recesses 13 penetrate the two end faces of the cathode current collector 11 in the width direction. Multiple strip-shaped protrusions 14 extend along the width direction of the cathode active material layer 12, and the multiple strip-shaped protrusions 14 extend to the two end faces of the cathode active material layer 12 in the width direction.

[0041] Furthermore, the structure of the cathode single-sided region satisfies the following relationship: S = (L1 - L0) / 2h; 5% ≤ (L1 - L0) / L0 × 100% ≤ 10%; where S is the number of strip-shaped recesses 13 or strip-shaped protrusions 14 on the cathode single-sided region 10; L1 is the length of the cathode single-sided region 10 after extension; L0 is the length of the cathode single-sided region 10 before extension; H0 is the vertical distance from the lowest point of the strip-shaped recess 13 to the plane of the cathode current collector 11 away from the cathode active material layer 12.

[0042] This invention satisfies the above-mentioned relationship by setting the structure of the cathode single-sided region 10. This structure can realize the residual compressive stress field induced by the curvature of the micro-curved surface to form a dynamic cancellation mechanism with the tensile stress generated by the expansion of the material during electrochemical cycling. Thus, the cathode electrode 20 containing the cathode single-sided region 10 of this invention will not break during the cycling process of the silicon-carbon system.

[0043] Specifically, 5%≤(L1-L0) / L0×100%≤10% indicates that the elongation rate of the single-sided region 10 of the cathode is 5%-10%. By limiting the elongation rate of the single-sided region 10 of the cathode, as well as the length before elongation, the length after elongation, and the depth of the strip-shaped recess, the number of strip-shaped recesses 13 and strip-shaped protrusions 14 on the single-sided region 10 of the cathode can be calculated. This ensures that the single-sided region 10 of the cathode does not break, and can better dynamically offset the tensile stress generated by the material expansion during electrochemical cycling, so that the cathode does not break during the cycling process of the silicon-carbon system.

[0044] Further, the length L0 of the cathode single-sided region 10 before extension is 100-200 mm; and / or, the length L1 of the cathode single-sided region 10 after extension is 105-220 mm. In the embodiments, the length L0 of the cathode single-sided region 10 before extension may be, but is not limited to, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, or 200 mm, and the length L1 of the cathode single-sided region after extension may be, but is not limited to, 105 mm, 110 mm, 115 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, or 220 mm.

[0045] Furthermore, the number S of the strip-shaped recesses 13 and / or strip-shaped protrusions 14 is 13-2000. When the number of strip-shaped recesses 13 / strip-shaped protrusions 14 is greater than 2000, the cathode single-sided area 10 is prone to breakage. When the number of strip-shaped recesses 13 / strip-shaped protrusions 14 is less than 13, the stress cannot be sufficiently dispersed, and there is a risk of aluminum foil transgranular or intergranular breakage.

[0046] Preferably, the number of strip-shaped recesses 13 is 13-500; and / or the number of strip-shaped protrusions 14 is 13-500. Specifically, the number of strip-shaped recesses 13 / strip-shaped protrusions 14 may be, but is not limited to, 13, 15, 20, 25, 30, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500.

[0047] During the lithium insertion / extraction process of silicon-carbon composite anode materials, the anisotropic stress generated by volume expansion easily leads to shear stress concentration at the interface between the current collector and the active material, especially in regions with abrupt changes in topological curvature such as the cell's radius (R-angle). By providing an appropriate number of strip-shaped recesses 13 and strip-shaped protrusions 14 (13–500 strips) in the cathode single-sided region 10, the stress originally concentrated in a single area can be dispersed into multiple structural units, thereby effectively alleviating the stress concentration effect and reducing the risk of transgranular or intergranular fracture of the aluminum foil.

[0048] The strip-shaped corrugated array provides excellent elastic deformation capability through its periodic structural design, enabling it to absorb mechanical energy and reduce damage to the current collector during repeated volume changes. Choosing a number range of 13–500 strips ensures sufficient buffering capacity while avoiding the problems of increased structural rigidity and decreased deformation coordination caused by excessive density, thus achieving excellent fatigue resistance and long-term cyclic stability.

[0049] By introducing multiple strip-shaped uneven structures at the microscale, the contact area and mechanical interlocking effect between the active material layer and the current collector are significantly increased, which helps to improve the interfacial bonding strength between the two. This design can effectively prevent the active material from falling off due to repeated expansion and contraction of silicon-based materials, ensuring the electrochemical stability and capacity retention of the battery.

[0050] The strip-shaped structures within this quantity range can be realized through existing micro-nano processing, imprinting, or template-assisted coating processes, exhibiting good manufacturability and process compatibility, which is conducive to promoting the industrial application of this invention in high-energy-density lithium-ion batteries.

[0051] In summary, by reasonably limiting the number of strip-shaped recesses 13 and strip-shaped protrusions 14, the adaptability and stability of the cathode single-sided region 10 structure under complex stress environments are further enhanced.

[0052] Furthermore, such as Figure 1As shown, the vertical distance H0 from the lowest point of the strip-shaped recess 13 to the plane of the cathode current collector 11 away from the cathode active material layer is 5-200 μm; and / or, the vertical distance H1 from the apex of the strip-shaped protrusion 14 to the plane of the cathode active material layer 12 away from the cathode current collector is 5-200 μm. Specifically, in the embodiments, H0 / H1 can be, but is not limited to, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, and 200 μm.

[0053] Silicon-carbon composite anode materials undergo volume changes of up to 300% during lithium insertion / extraction, leading to significant anisotropic expansion and substantial shear stress at the interface between the current collector and the active material. By controlling the heights of the strip-shaped recesses 13 and convex sections 14 within the range of 5–200 μm, a three-dimensional structure with a certain buffering capacity can be formed at the microscale. This absorbs the mechanical stress generated by the volume change, reduces the risk of shear failure at the interface, and improves the mechanical stability of the electrode structure.

[0054] This highly designed structure gives the striped, corrugated array excellent elastic deformation capabilities, allowing it to undergo moderate deformation without structural damage during repeated expansion and contraction of the silicon-based material. This characteristic helps maintain a stable bond between the current collector and the active material, preventing interface degradation caused by structural fatigue or fracture, and extending battery cycle life.

[0055] The strip-shaped uneven structure, at a certain height, can significantly increase the contact area and mechanical anchoring effect between the active material and the current collector, thereby improving the interfacial bonding force between them. This enhanced interfacial bonding ability can effectively suppress the delamination of the active material caused by volume changes, ensuring the stability of the battery's electrochemical performance during long-term cycling.

[0056] In silicon-carbon composite anode systems, stress concentration in localized areas is a particularly prominent issue, especially in regions with abrupt geometric changes such as the cell's radius (R-angle). By incorporating strip structures with heights ranging from 5 to 200 μm, effective control of localized stress can be achieved without significantly increasing the electrode thickness. This prevents transgranular or intergranular brittle fracture of the aluminum foil, thereby improving the overall structural reliability.

[0057] This height range can be achieved through existing mature microstructure forming processes such as imprinting, template-assisted coating, and laser processing. This not only meets the needs of functional structure design, but also does not impose excessive difficulty or cost burden on the electrode fabrication process, which is conducive to promoting the engineering application of this technology in high-energy-density lithium-ion batteries.

[0058] In summary, by reasonably limiting the height of the strip-shaped recess 13 and the strip-shaped protrusion 14 (5–200 μm), the buffering capacity and structural stability of the cathode single-sided region 10 under complex stress environment are further enhanced.

[0059] Furthermore, the cross-sections of the strip-shaped recess 13 and the strip-shaped protrusion 14 are elliptical or polygonal, and the polygons can be triangles, rectangles, pentagons, hexagons or other irregular polygons.

[0060] This embodiment also provides a cathode electrode 20, which includes the aforementioned cathode single-sided region 10, wherein the cathode single-sided region 10 is located at one end of the cathode electrode 20 along its length.

[0061] This embodiment also provides a secondary battery, including an electrode assembly, which includes the aforementioned cathode electrode. Specifically, the electrode assembly includes an anode electrode, a separator disposed on the surface of the anode electrode, and a cathode electrode disposed on the side of the separator away from the anode electrode. A single-sided cathode region is disposed at one end of the cathode electrode along its length, with the side of the single-sided cathode region coated with a cathode active material layer close to the separator, and the side of the single-sided cathode region not coated with a cathode active material layer away from the separator.

[0062] Furthermore, the electrode assembly is a wound electrode assembly, with the cathode single-sided area located at the outermost ring of the electrode assembly. Specifically, the side of the cathode single-sided area not coated with the cathode active material layer is located at the outermost edge of the electrode assembly, while the side of the cathode single-sided area coated with the cathode active material layer faces the interior of the electrode assembly. The secondary battery of this invention does not experience cathode breakage during silicon-carbon system cycling and can store more electrolyte.

[0063] This embodiment also provides an electronic device including the aforementioned secondary battery. In this embodiment, the electronic device can be, but is not limited to, various portable electronic devices (such as smartphones and laptops), power tools, new energy vehicles, and other end products with high requirements for energy density, cycle life, and safety.

[0064] The above embodiments are preferred implementations of this utility model. In addition, this utility model can also be implemented in other ways. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this utility model.

Claims

1. A single-sided cathode region, characterized in that, The device includes a cathode current collector and a cathode active material layer coated on one surface of the cathode current collector. A strip-shaped corrugated array is provided on one side of the cathode. The strip-shaped corrugated array includes multiple strip-shaped recesses and multiple strip-shaped protrusions. Multiple strip-shaped recesses are located on the surface of the cathode current collector away from the cathode active material layer, and are spaced apart along the length of the cathode current collector. Multiple strip-shaped protrusions are located on the surface of the cathode active material layer away from the cathode current collector, and are spaced apart along the length of the cathode active material layer. Each strip-shaped protrusion corresponds to one of the multiple strip-shaped recesses.

2. The cathode single-sided region according to claim 1, characterized in that, The structure of the single-sided region of the cathode satisfies the following relationship: S=(L1-L0) / 2h; 5%≤(L1-L0) / L0×100%≤10%; Wherein, S is the number of the strip-shaped recesses or strip-shaped protrusions on the single-sided cathode region; L1 is the length of the extended single-sided region of the cathode; L0 is the length of the cathode single-sided region before extension; H0 is the vertical distance from the lowest point of the strip-shaped recess to the plane of the cathode current collector that is away from the cathode active material layer.

3. A single-sided cathode region according to claim 2, characterized in that, The length L0 of the cathode single-sided region before extension is 100-200 mm; and / or, The length L1 of the extended single-sided cathode region is 105-220 mm.

4. A single-sided cathode region according to claim 3, characterized in that, The number of the strip-shaped recesses is 13-2000; and / or the number of the strip-shaped protrusions is 13-2000.

5. A single-sided cathode region according to claim 4, characterized in that, The vertical distance from the lowest point of the strip-shaped recess to the plane of the cathode current collector away from the cathode active material layer is 5-200 μm; and / or, the vertical distance from the apex of the strip-shaped protrusion to the plane of the cathode active material layer away from the cathode current collector is 5-200 μm.

6. A single-sided cathode region according to claim 1, characterized in that, The cross-sections of the strip-shaped recess and the strip-shaped protrusion are elliptical or polygonal.

7. A cathode electrode, characterized in that, Includes the single-sided cathode region as described in any one of claims 1-6, wherein the single-sided cathode region is located at one end of the length direction of the cathode electrode.

8. A secondary battery, characterized in that, It includes an electrode assembly, the electrode assembly including the cathode electrode of claim 7.

9. The secondary battery according to claim 8, characterized in that, The electrode assembly is a wound electrode assembly, and the cathode single-sided area is located at the outermost ring of the electrode assembly.

10. An electronic device, characterized in that, Includes the secondary battery as described in claim 8 or 9.

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